Shaft efficiency monitoring system

ABSTRACT

A system for continuously providing direct readouts of horsepower and efficiency of a rotating shaft, which includes a husk assembly associated with the shaft and providing electrical signals proportional to shaft torque, a tachometer for providing electrical signals proportional to shaft rotational speed, electrical circuitry for electronically multiplying the torque signals by the RPM signals to determine shaft horsepower, and a dividing network for dividing the shaft horsepower signal into an electrical signal representing the rate of fuel consumption to provide a continuous indication of instantaneous system efficiency.

This is a division of application Ser. No. 469,900, filed May 14, 1974.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to horsepower indication and monitoringsystems, and more particularly, to apparatus for continuously,electronically monitoring the horsepower being transmitted through ashaft as well as operating efficiency of the drive engine causing suchrotation.

2. Descripton of the Prior Art

Numerous situations exist where a shaft is rotated by an appropriatedrive mechanism to perform useful work. Exemplary of the same areelectric power plants, industrial machine drive systems,propeller-driven ships, and the like. In all of these systems, and infact in any system in which a powered prime mover causes the poweredrotation of a driving shaft, it is extremely important to effectivelymonitor the horsepower being transmitted through the shaft as well asthe overall efficiency of the system including the prime mover, theshaft, and the ultimate output assembly.

In connection with propeller-driven ships, it is extremely importantthat monitoring equipment simply, yet effectively provide accurate andcontinuous indications of the horsepower being transmitted through theship's propeller shafts in order to enable the ship's operatingpersonnel to obtain the optimum performance for developing the maximumoutput with the least consumption of fuel. While this may be arelatively minor task in connection with small pleasure craft, itbecomes a substantial undertaking in connection with large commercialships such as ocean liners, freighters and tankers. In these latterinstances, measurements must be undertaken from one or more enginescapable of producing many thousand horsepower and transmitting suchpower through propeller shafts often many city blocks long and weighingmany tons. Yet, these measurements must be accurate, reliable and rapid.

The advantages in installing a shaft horsepower monitoring system aremany. From the horsepower and the efficiency information data providedby such system, the operator can readily verify the ship's efficiency,potential faults, and system overloads so as to prevent damage to theassembly and to extend periods between costly overhauls. The data soobtained reduces operating costs, fuel consumption, down time andmaintenance, thereby increasing both the ship's reliability and itsoverall efficiency.

It is also well known to those familiar with large scale propellerdriven ships, that where such ships have two main propeller shafts, itis manifestly important that both propellers transmit exactly the sameamount of power while underway. While RPM is often used as a closeestimate of power being transmitted through the shaft, the same is atbest an approximation since the actual amount of power being transmittedthrough the shaft is affected by many variables such as propellerefficiency, blade angle and diameter. Thus, especially with pluralshafts, it is important to monitor the actual power being transmittedthrough the same since unequal power transmission will inherently causepower drive steering action which, thereafter, would have to becorrected by changing the rudder angle. This develops unnecessary powerdissipation from rudder drag with corresponding waste of fuel.

It is also particularly desirable to examine the actual horsepower beingtransmitted through a ship's propeller during the conducting of seatrials for ship's performance. Large ships for both military andcommercial applications must undergo rigorous sea trials at which timedata pertaining to virtually every phase of ship's operation is compiledand analyzed before required certification is issued. In theseinstances, apparatus is necessary to effectively monitor, on a continualbasis, the horsepower and fuel consumption efficiency of the ship'spower plant while at the same time allowing a permanent recording ofsuch obtained data to be made.

While the prior art, as exemplified by my U.S. Pat. No. 3,274,826, isgenerally cognizant of systems for directly enabling readout of shafthorsepower, such systems have proven to be only partially satisfactory.This is due to the fact that such systems are typically quite complex,include mechanical sub-systems and/or servo feedback loops, are verycostly, are slow responding, are comparatively large, require anull-balance system with wearable precision potentiometers and rotatingmechanical members and cannot be manufactured by integrated, electroniccircuit techniques. Thus, a versatile, economical and fully effectivemonitoring system to meet the needs of today's marine engineer as wellas other concerned with the transmission of power through rotatingshafts has heretofore been unavailable.

SUMMARY OF THE INVENTION

It is, therefore, a primary object of the present invention tocontinuously, accurately, and effectively determine and provide aperceptible readout of the actual horsepower output through the poweredshaft of a prime mover, such as the propeller shaft of a ship, as wellas overall system efficiency or fuel rate economy.

The present invention, in one aspect, can be summarized in that a systemfor determining the power being transmitted through a rotated shaftincludes a first assembly coupled with the shaft for generating a directcurrent signal proportional to torque through said shaft, a secondassembly coupled with the shaft for generating a direct current signalproportional to shaft RPM, and an electronic circuit connected toreceive the generated direct current signals from the first and secondassemblies, respectively, for electronically multiplying such signals toproduce a direct current signal linearly representative of thehorsepower actually being transmitted through the shaft.

Another object of this invention is to construct a totally electronichorse-power and efficiency monitoring system capable, at least in part,of integrated circuit fabrication.

The present invention has a further object in the monitoring andcontinuous calculation of instantaneous specific fuel rate of the primemover of a rotated shaft.

Another object is to monitor a power rotated shaft system and togenerate in response thereto analog and/or digital readout indicationsof shaft horsepower, as well as indications of totalized shafthorsepower-hours and graphical shaft horsepower versus time traces.

The present invention provides numerous improvements and advantages overthe prior art in that all computations are electronic, direct, andautomatic, that high precision readings are facilitated, that mechanicaland servo-type mechanisms are eliminated, that indications of both shafthorsepower and instantaneous specific fuel rate are provided, that allreadout measurements are extremely rapid, that over-torque and reversetorque indications are provided, and that the overall system is compact,light weight and economical to manufacture. Furthermore, the presentinvention is advantageous in that the same is adaptable to modularconstruction, and includes a husk assembly for deriving torque inputsignals, which husk assembly is light weight, is positively supportedabout a shaft to minimize vibration and shock, and may be constructed ofnon-ferromagnetic material allowing the use of electromagnetic pick-upswithout disturbance.

These and other objects and advantages of the present invention will bemore fully appreciated when taken in conjunction with the accompanyingdetailed description of a preferred embodiment and the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view of a preferred embodiment of a shafthorsepower and efficiency monitoring system according to the presentinvention;

FIG. 2 is a side elevational view of the husk assembly of the system ofFIG. 1, with parts broken away and parts illustrated in section;

FIG. 3 is a sectional view taken on line 3--3 of FIG. 2;

FIG. 4 is a detail view of the husk assembly of FIG. 2 with parts brokenaway and parts shown in section;

FIG. 5 is a partial elevational view, with parts in section, taken alongline 5--5 of FIG. 4;

FIGS. 6A 6B, and 6C are schematic diagrams which, taken together,illustrate the electrical circuit of the system according to the presentinvention;

FIG. 7 is a schematic diagram of the electrical circuit of the huskassembly of FIG. 2;

FIG. 8 is a schematic diagram of the multiplier of the circuit of FIG.6; and

FIG. 9 is a block diagram of the divider network of the circuit of FIG.6.

DETAILED DESCRIPTION OF THE INVENTION

While the present invention has utility in connection with any number ofvarious systems in which it may be desired to determine, indicate, andrecord the shaft horsepower and/or instantaneous specific fuel rate of aprime mover driven rotated shaft, for exemplary purposes only theinvention will be described and illustrated herein in conjunction with apreferred embodiment adapted specifically for use in connection withmonitoring the propeller shaft of a ship. It is therefore to beunderstood that the present invention is not limited or restricted toany one particular system, but is intended for use generally for thepurpose of determining the horsepower delivered by any powered shaft andthe efficiency of the prime mover associated therewith.

Before proceeding with a detailed description of the preferredembodiment, it is believed helpful to briefly describe the theory ofoperation of the present system particularly as it relates to monitoringof propeller driven ships.

To fulfill the requirements in measuring shaft horsepower developed inthe main shaft of an engine, namely, the propeller shaft in a ship, itis necessary to derive signals repesentative of the variables set forthin the shaft horsepower formula which reads as follows: ##EQU1## WhereinSHP equal shaft horsepower, RPM equals shaft revolutions per minute, andthe figure 5252 represents a constant.

This formula represents the instantaneous readout of horsepower at anyone moment, the horsepower output varying considerably from moment tomoment with variations in torque or speed. In order to satisfy thisequation, it is readily apparent that a monitoring system must becapable of deriving accurate signals indicative of both shaft RPM andshaft torque.

The present system derives a direct current signal representative ofshaft RPM by means of a tachometer generator mechanically coupled to theshaft for detecting rotations thereof. The development of a signalrepesentative of shaft torque is a somewhat more complex matter andconsists essentially in the generation of a variable signal voltageproportional to propeller shaft twist resulting from the torque appliedto the shaft by the prime mover. By modulating an oscillating signal inproportion to such detected torsional shaft flexure, and by demodulatingthe same to provide a direct current output signal, such signal may beaccurately considered to represent actual torque experience by a shaftsince the absolute value of torque is related to shaft flexure by aconstant dependence upon the modulus of rigidity of the shaft, its size,and material employed in construction.

As is well known, the modulus of rigidity represents the ability of theshaft to resist the twisting forces developed by the torque exerted inthe main shaft when an engine is driving the propeller to move the ship.Thus, once the modulus of rigidity, shaft diameter and shaftconstruction is known, the detected amount of twist, which is extremelysmall, that takes place in the shaft is directly proportional to thetorque in a shaft and follows in a linear pattern over the range oftorque applied for propulsion. In other words, the maximum torque doesnot normally exceed the elastic limits of the shaft.

Although the torque in a rotating member is in a circular direction, theamount of twist or flexure that takes place is so small that even thoughthe precise measurement is along an arc on the shaft surface, nomeasurable error is introduced when this torsional shaft flexure isevaluated as a linear displacement along a chord subtending this radialarc. This is due to several reasons. First, in large ships of the typefor which the present system is primarily advantageous, the radius ofpropeller shaft is quite large when compared to the arc traversed duringtwisting. Second, when a linear variable differential transformer isused to detect actual movement, the same is unaffected by lateralshifting or rotating in directions other than the direction of the twistsuch that average resultant readings are unchanged.

The modulus of rigidity in any particular shaft can be readilyascertained by known methods using specific weights to load the shaftand comparing actual twisting with modulus of rigidity tables providedby the shaft manufacturer and based upon the alloyed steel and type ofheat treatment involved. Thereafter, by calibrating the flexuredetection assembly, the direct curent output signal provided by the samecan be made directly proportional to and representative of actual shafttorque.

Since, as described above, the modulus of rigidity of any particularshaft may be readily computed, it is therefore only necessary to measurethe magnitude of the twist in the shaft over a specific distance whichreflects the torque under load. To accomplish this, the system inaccordance with the present invention includes a husk assemblymechanically configured about the shaft and clamped to the shaft betweentwo annular knife edges, one on each end. The husk assembly is laterallysplit at approximately its mid point such that the two sections thereofmay be rotatably displaced with respect to each other in proportion tothe degree of twisting exhibited within the length of shaft between theannular knife edges. As noted above, in accordance with the presentinvention, a direct current signal is generated in proportion to thisdetected twisting and fed along with the signal repesentative of shaftRPM to a solid state electronic multiplying network which generates, atan output, a signal representative of the product of these twovariables. Accordingly, this output signal is directly and linearlyproportional to shaft horsepower and can be used to drive any desiredindicating network.

In addition to the foregoing, the signal derived by the multiplyingcircuit is also fed as the denominator to a dividing circuit, whichreceives at its numerator input a direct current signal proportional tothe instantaneous rate of fuel flow. The dividing network is preferablyconstructed of solid state components either as a discreet or integratednetwork, and accurately and continuously computes a rate of fuel flowper shaft horsepower so as to indicate the instantaneous specific fuelrate or system efficiency of the apparatus under examination.

Turning now to FIG. 1, the same diagrammatically represents the overallsystem in accordance with the present invention and includes a controlpanel 100 housing all of the primary electrical circuitry, controls andindicator lamps, for operating the system. Power for the system isderived from a suitable source of AC operating potential 102 which isfed through an on-off control switch 104 to the rest of the circuit. Apower indicator lamp 106 apprises an operator of the operating status ofthe system. The control panel also includes a switch 108 having a firstposition for normal system operation and a second position substitutingpre-selected calibration signals to the system meters. Positioning ofswitch 108 into the second position is indicated by appropriate alarmindicator 110 mounted on the panel next to switch 108.

An overtorque alarm lamp 112 and an astern torque indicator 114 are alsomounted on the panel to inform the operator of these eventualities.Also, another switch 116 allows both RPM and torque signals to bereversed in polarity, reversal being indicated by an "astern" indicatorlamp 118. RPM and torque meters 120 and 122, respectively, arecalibrated for direct read-out of the RPM and torque signals of thesystem, and may be used for system calibration.

Three distinct input signals are provided to the circuitry housed withinthe control panel 100. The first is derived from a husk assembly 200,which will be described in detail below. Husk assembly 200 receivesregulated DC operating potential along lines 202 and 203 and applies thesame through a brush and slipring assembly to a twist detection networkwhich produces direct current signals on lines 204 and 205representative of system torque.

Mechanically coupled to the rotating shaft at the husk assembly 200 is atachometer generator 206 which provides a direct current output signalon lines 207 and 208 representative of shaft RPM. Also, a flow meter210, of any suitable construction, is interposed in the main fuel supplyline for the ships propulsion engine and delivers a DC output signal onlines 211 and 212 which is representative of the rate of fuel flow tothe engine. The output signals on lines 204-205, 207-208, and 211-212,which are representative of torque, RPM, and fuel consumption,respectively, are all connected to the control panel assembly throughappropriate interconnecting cables for subsequent electronic processing.

Circuitry in the control panel, as will be described more fully below,processes the input signals fed thereto so as to derive output signalsrepresentative of shaft horsepower and instantaneous specific fuel rateor efficiency. Signals representative of shaft horsepower are coupledvia lines 300 and 301 to a strip chart recorder 302 which, as is wellknown, includes an elongated sheet of graph paper driven at a constantspeed and cooperating with a pen moved in response to the amplitude ofreceived signals to provide a permanent recording of variations in shafthorsepower vs. time. It is also noted that recorder 302 may contain anynumber of pens, with different colored ink, each being connected toreceive input signals representative of the horsepower within pluralshafts of the ship for providing a continuous permanent record ofsimultaneous horsepower readings of the plural shafts.

The shaft horsepower signal is also fed via lines 303 and 304 to adigital integrator 305 which integrates or totalizes such input signalsand provides a direct digital readout of shaft horsepower-hours. Thismeasurement is particularly useful in making long term analyses ofoverall system efficiency. For example, the totalized readout of thedigital integrator 305 after 1 hour of ship operation may be dividedinto the number of pounds of fuel which were consumed during that hourto readily determine the average specific fuel rate during that period.

Of course, the shaft horsepower signals are in addition fed over lines306 and 307 to an analog shaft horsepower indicator meter 308 having acalibrated dial for direct readout of shaft horsepower. While analogmeter 308 is particularly advantageous when it is desired not only toreadout shaft horsepower but to rapidly enable visual perception ofshaft horsepower fluctuations with time, greater accuracy in actualshaft horsepower readout can be achieved by using any suitable digitalindicator 310 either in parallel with or in lieu of the analog meter308.

In addition to the above indicators, for providing various readouts ofshaft horsepower, the control panel circuitry also electronicallycomputes instantaneous specific fuel rate or system efficiency byelectronically dividing the rate of fuel consumption signal by the shafthorsepower signal and generating a DC output signal in response thereto.This output signal is applied over lines 311 and 312 to a specific fuelrate indicator 313. The specific fuel rate indicator provides an analogreadout of instantaneous specific fuel rate or system efficiency andincludes two calibrated scales, with such calibration obtained bycomparison of actual measured data with theoretical or expectedreadouts.

It is envisioned that the control panel as well as recorder 302, digitalintegrator 305, shaft horsepower meters 308 and/or 310, and specificfuel rate indicator 313 would all be mounted at a suitable controlstation within the ship's engine compartment. Since the ship's engineeris responsible for maintaining efficient operation of the main engines,the fact that all of the apparatus is located within the engine roomeffectively provides the engineer with the data necessary for him toaccomplish the desired result. Of course, it may often be desired toprovide additional indicators or meters directly at the ship's bridgeespecially on modern ships having direct bridge controls of the mainengines.

Turning now to the details of the husk assembly 200, as shown in FIGS. 2through 5, the same consists of first and second generally cylindricalportions 213 and 214 each in the form of a semi-circular half clampedtogether around the ships propeller shaft 215. Each half section 213 and214 is capable of moving independently free of the other half, and isrigidly fastened to the shaft 215 on their outside ends by annularknife-edge collars 216 and 217, respectively. Collars 216 and 217 areattached to the cylindrical husk portions 213 and 214 by any suitablemeans, such as by threaded fasteners, so that the overall assemblyrotates with the shaft.

Along the inner or adjacent peripheral boundaries of sections 213 and214 are disposed a plurality of low friction bearing pads 218 extendingfrom shell portions 213 and 214 so as to rest against the shaft surface.These bearing pads may be provided in the form of continuous bands ordiscrete sections, with approximately 12 sections peripherally disposedin equispaced arrangement being preferred. On initial installation, thehusk assembly is disposed about the shaft and the semicircular halvesthereof joined by suitable connecting bolts 219 and 220. Bolts 219 arethen securely tightened in order to rigidly clamp the annular collars216 and 217 against the shaft. On the other hand, bolts 220 are gentlytightened and backed off so as to provide a very slight space betweenthe bearing pads and the shaft surface. Spacing bolts 221 are thenadjusted to maintain the bearing pad spacing, with bolts 220subsequently securely tightened to complete the assembly.

Bearing pads 218 may be of any suitable construction exhibiting thecharacteristics of high mechanical strength and durability with lowfriction. Exemplary of such pads are those sold under the trademarkOilite and formed of sintered or powdered bronze filled with a lubricantsuch as oil.

Temporary spacers, not shown, are used during the installation procedureto provide a gap or opening between the husk assemblies 213 and 214 foraccommodating the torque detecting assembly illustrated in detail inFIGS. 4 and 5. This assembly includes a housing 222 containing theelectrical circuitry illustrated in FIG. 7 and described below. Housing222 is preferably carried upon a flange of husk assembly 213 and iselectrically connected to a linear variable differential transformer223. Transformer 223 is attached by a flange 224 to husk assembly 213and cooperates with a soft iron core 225 slidably disposed in a housing226 attached to husk section 214. In this manner, relative movementbetween husk assembly sections 213 and 214 due to twisting or torsionalflexure of the shaft 215 will cause linear displacement of the core 225with respect to the transformer windings 223.

Core 225 is attached to an internally threaded sleeve 227 slidablydisposed in housing 226 and cooperating with a key 228 to precluderotation. An adjusting bolt 229 is threadedly received within sleeve 227and carries a circular scale 234 enabling calibration of thetransformer. Bolt 229 and scale 230 are retained in the positionillustrated in FIG. 4 by a retaining member 232 which also functions asa clamp to prevent the apparatus from going out of calibration. Withinthe lead screw housing is a compression spring 233 that continuallypresses against the female portion of the lead screw assembly in onedirection so as to eliminate any backlash when reversing rotation of thescrew thereby avoiding errors in calibration.

The transformer includes three coil windings to effect a change involtage when the core is moved with regard to direction and magnitude.The three windings comprise a primary winding which induces power intothe secondary windings and two secondary windings one each for the twodirections of movement. When there is zero torque in the main shaft, thecore is located at a mid point neutral position within the two secondarycoil windings producing a zero differential voltage readout. This causesthe provision of a null or a zero readout to indicate that the core isin a neutral position for zero torque.

The core in the transformer is made of soft iron which magneticallyeffects the transformation of current between the primary and secondarywindings to produce the above noted readout. When there is an unbalancein the transformer due to displacement of the core, the magnitude of thevoltage readout is the resultant output between the two opposingsecondary coils, which is directly proportional to coaxial displacementof the coil within its housing. In practice, the core itself is only aportion of the shaft extending through the windings, the remainingsections of the shaft being formed of non-magnetic materials.

The lead screw 229 and calibration dial 230 are precisely machined formaking accurate calibrations of the system. Calibration dial is usedonly when making zero adjustments and for determining the transformerratio and its calibration figure while comparing it to the torqueindicating meter readout. The formula for shaft deflection in lead screwdial divisions from torque only, with known modulus of rigidity, radiusof the shaft, length of and husk between clamping planes, and radius oftransformer core is as follows: ##EQU2## where Δ equals the deflectionin divisions on the shaft dial where the lead screw has a 0.025 inchpitch, t equals torque in pound-inches, l equals length between clamps216 and 217, b equals radius in inches (distance of transformer corefrom center), c equals modulus of rigidity in pounds per square inch, r₁equals radius to outside diameter of shaft in inches, and r₂ equalsradius to inside diameter of shaft in inches (0 for a solid shaft).

The zero torque position can be set in using the lead screw and dial toaverage out the residual torque remaining in the shaft for both theahead and astern torque meter readout by alternately "jacking" (puttingtorque into the shaft) the shaft in both these directions.

Turning back to FIGS. 2 and 3, an appropriate cover assembly 234 mayencircle the gap between husk sections 213 and 214 to preclude the entryof dust and other foreign particles therebetween and may be attached byany suitable fastening means on one of the two husk sections. Husksection 213 also carries four sliprings 235, 236, 237, and 238 forcooperation with a brush assembly 239 of any well known construction.The brushes and sliprings cooperate to enable direct current inputsignals and direct current output signals to be communicated with therotating husk assembly during operation of the ship.

The shaft speed is obtained by use of the direct current tachometergenerator 206 which is coupled to and driven by the main shaft todevelop a gradient of electrical voltage directly proportional to thespeed in RPM. It is preferred that the generator 206 include a permanentmagnet field which reverses the output polarity with respect todirection change in shaft rotation. As shown in FIG. 2, the generator ismounted adjacent the shaft and is connected thereto through gears sothat it runs at a considerably higher speed than the main shaft RPM.Rather than using expensive large gears, incorporated onto one end ofthe husk steel plate 217 are embedded a plurality of steel pins whichmesh with the teeth of a spur gear 252 attached to the generator shaft.The number of pins installed on the husk and the amount of teeth on themating spur gear is a function of overall gear ratio to develop theproper voltage gradient with respect to the expected range of shaftspeeds.

Turning now to FIGS. 6a, 6b, and 6c, power from AC source 102 is appliedby lines 103 through power switch 104 to a pair of fuses 123. Neonindicator lamps 124 are connected in parallel with fuses 123 to indicatethe occurrence of a blown fuse. The other side of the pair of fuses 123is connected to main AC power lines 125 across which is connected on-offindicator lap 106 and the coil of a power failure relay 126. Relay 126includes appropriate normally open and normally closed connections forintercoupling with an external alarm to indicate power failure. Lines125 are also connected to the input windings of an isolation transformer127 in a voltage regulated DC power supply identified generally as 128.The output of transformer 127 is fed through a rectifier network 129 anda bank of filter condensers 130 to two identical solid state regulatornetworks 131 and 132. Three output terminals are therefore provided onesupplying positive 15 volts DC, one supplying negative 15 volts DC andthe other acting as common for both positive and negative terminals.Power supply 128 supplies a very accurately regulated DC output signalso as to facilitate accurate measurements within the system. Theregulator 128 in cooperation with isolation transformer 127 effectivelyshields the entire system from inaccuracy and disturbances frequentlyencountered in the AC power supplies on board a ship.

The plus and minus 15 volt DC output terminals of the regulator 128 arerespectively connected via lines 133 and 134 to two of the brushes ofthe husk assembly. As will be described below, the DC operatingpotential on lines 133 and 134 is fed to activate the circuitry withinthe husk assembly which thereafter generates a fluctuating DC signal fedthrough brushes to lines 135 and 136 and proportional to shaft torque.The torque DC signal, which is proportional in magnitude and polarity tothe amplitude and direction of shaft torque, is fed over lines 135 and136 to a potentiometer 137 which enables pre-selection of an over torquethreshold for actuating the coil of an over torque relay 138. Overtorque alarm lamp 112 is connected through the contacts of relay 138across the secondary of a step-down transformer 139 so as to becomeenergized upon receipt of a torque signal exceeding the pre-selectedthreshold.

The DC torque signal on lines 135 and 136 is also fed through diodes 140and 141 to an operational amplifier 142 which in turn drives asterntorque indicator rectifier 143. A relay and filter network 144 receivesoperating potential from the secondary of transformer 139 for providinga sufficiently high direct current potential to selectively actuate thecoil of the astern torque indicator 143 under the control of amplifier142. Lamp 114 of the control panel is connected across the secondary oftransformer 139 through the contacts of relay 143 such that an outputindication will be provided whenever a negative DC torque signal isgenerated by the husk assembly.

Output signals from the husk assembly on lines 135 and 136 as well asthe output signals provided by the DC tachometer generator 206 on lines207 and 208 are fed through suitable level setting potentiometers to thex and g inputs of a solid state 4 quadrant analog multiplier 145. Thetorque and RPM signals are supplied to the multiplier 145 through switch108 which, in the position illustrated provides direct interconnectionof the signals to the multiplier. In the check test position, switch 108disconnects the input signals from the husk assembly and tachometergenerator and substitutes therefor signals on lines 146 and 147,respectively from torque and RPM adjusting potentiometers 148 and 149,respectively connected to the power supply 128. In this manner,preselected or standardized test voltages may be readily andconventiently provided as inputs to the multiplier 145 for calibrationand test purposes. The various signals including the power supplyvoltage, the torque check test voltage, and the RPM check test voltagemay also be examined by external meter means via the test point panel150 provided within the control panel.

Switch 116 is connected to supply the stepped down AC output oftransformer 139 to the operating coil of a reversing relay 151. In theposition illustrated, switch 116 isolates the coil of relay 151 fromtransformer 139 whereupon relay 151 assumes its normal or quiescentstate as shown. In this state, torque and RPM signals on lines 135-136and 207-208 are directly connected through conventional diode protectionnetworks to the torque indicating and RPM indicating meters 122 and 120,respectively. When switch 116 is moved to its astern position, ACpotential from transformer 139 is fed to the coil of relay 151 actuatingthe same and causing reversal of the connections to the torque and RPMindicating meters 122 and 120.

The leftmost pole of check test switch 108, as illustrated, isinterposed in one side of the supply connections between transformer 139and the coil of relay 151 such that transposition of the switch 108 tothe check test position immediately causes relay 151 to revert to itsnormal or quiescent state regardless of the position of switch 116.After check test measurements and adjustments are made, and the switch108 is moved back to its indicating position, the meters 122 and 120 areconnected again in accordance with the ahead or astern position selectedby switch 116. It is further noted that lamp 118 is connected across theoutput of transformer 139 through an additional set of contacts ofswitch 116 so as to become illuminated whenever switch 116 is in theastern position. Check test alarm lamp 110 is similarly connectedthrough switch

The output of the solid state multiplier 145 is fed by a line 152 to thedata logger or recorder 302, the shaft horsepower indicator meter 308and the digital integrator 305. Integrator 305 includes a potentiometer153 connected in series with a resistor 154 across a DC motor 155. Theoutput shaft of the DC motor 155, which rotates in proportion to theamplitude of the input potential drives a 7 digit decade counter 156. Anilluminating lamp 157 is connected to the output of transformer 139 soas to facilitate visual perception of the totalized shafthorse-power-hours appearing on the decade counter 156.

The DC output signal on line 152, which is directly proportional to andis representative of shaft horsepower, is also applied through a DCamplifier 158 to the denominator input, X of a solid state dividernetwork 159. The numerator input, Z of divider 159 receives the directcurrent output signal of the flow meter 210 whereupon the dividerproduces a DC output signal on line 160 which is representative of theinstantaneous specific fuel rate or overall efficiency of the ship'spropulsion system. The signal on line 160 is fed through a diode andpotentiometer adjusting network to the specific fuel rate meter 313 soas to provide a continuous indication of instantaneous system efficiencyduring operation.

Both the multiplier network 145 and the divider network 159 arepreferably solid state modules fabricated by integrated circuittechniques. Moreover, these circuits accept direct current input signalsand produce direct current output signals whereby problems associatedwith alternating current systems such as harmonics, phasing, impedencemismatching and quadrature-null complications are avoided.

Referring now to FIG. 8, an exemplary circuit for multiplier 145 isshown and is of the variable transconductance type which exhibitsextremely favorable characteristics with respect to reliability,stability, accuracy, linearity, temperature, gain, offset errors, andinsensitivity to differences in input impedence. The multiplier is ananalog device of the transconductance type for precision two or fourquadrant application with adjustable gain and correction for offset.Since circuits of this general type are known to those of skill in theart, a detailed description will be omitted for the sake of brevity.However, it is noted that the variable transconductance multiplier ofFIG. 8 produces the product of input signals by varying thetransconductance of the transistors 161 and 162 so as to modulate theemitter current of transistor 163. Since the transconductance value of atransistor is proportional to the relative amount of collector currentflowing therethrough, the voltage gain of a transistorized differentialamplifier can be varied in accordance with such emitter current.Therefore, the cooperative interaction of transistors 161, 162 and 163results in the provision of an output signal directly related to theproduct of the two input signals applied to the network.

As shown in FIG. 9, the solid state divider network 159 is basicallysimilar to the multiplier circuit of network 145 and, thus, is shown inblock form only for exemplary purposes. The X and Z inputs to thedivider 159 are applied respectively to a log type inverter and avoltage to current transducer which provide output signals to atransconductance section 164. The output of the transconductance sectionis applied through an operational amplifier 165 as the dividend of thedivision Z/X.

The husk assembly circuitry is shown in schematic form in FIG. 7 andincludes a polarity reversal protecting transistor 240 which receivesthe direct current supply from the regulated power supply 128 andsupplies operating power to an oscillator circuit 241 which utilizes atransistorized chopper to energize the primary winding of the linearvariable differential transformer 223 with an alternating current havinga frequency of betwen 2500 to 10,000 Hz. The coaxial position of thecore 225 determines the gradient of voltage induced into each of theillustrated secondary windings. Each of the two secondary windings areconnected to a demodulator which consists of two single rectifiers forhalf wave rectification terminating in an RC filter section. Thesecondary windings are connected in series for rectified voltageopposition so that the resulting differential between the twosecondaries is a polarity selective direct current voltage proportionalto the core displacement from the electrical null position. Thedifferential output is connected to an operational amplifier 242characterized in that the output of the amplifier has a polaritydependent upon which of the input terminals receives the higher positivepolarity voltage. The amplifier 242 is thus both inverting andnon-inverting dependent upon the magnitude of the signals supplied asinputs thereto.

The magnitude of voltage amplification of amplifier 242 is dependentupon the resistance in the feedback resistor 243. Thus, the output ofamplifier 242 is a voltage which is directly proportional to torque andthe polarity is a function of relative core positioning with respect toa central position. The direct current output voltage signal of theamplifier 242 is then applied over lines 204 and 205 to leads 135 and136 of the control panel.

With shaft reversal, the RPM and torque polarities reverse butcorrespond to each other to produce upscale readouts.

Thus, it can be appreciated that the present invention provides a systemfor rapidly, efficiently and effectively monitoring and examining thehorsepower being transmitted through a rotating shaft as well as thespecific fuel rate or efficiency of the overall system. This isextremely important in conjunction with the propulsion of large shipsand satisfactorily resolves numerous problems experienced forconsiderable time in this art. It can be appreciated that the presentsystem provides no mechanical or complex servo feedback loops, isreadily adaptable to light weight, compact solid state integratedcircuit fabrication, and relies upon DC signals throughout for increasedaccuracy and elimination of phasing and impedance mismatching problems.Furthermore, the husk assembly is particularly advantageous in that themain body section thereof is fabricated from rugged cast aluminum andhas high strength steel clamping plates on the axial ends thereof wherestresses are highest. This arrangement provides light weight by usingaluminum for the non-stressed section while the clamps have tightstrength, durability, stability and ductility. This construction andassembly leads itself to lower costs and ease in machining, and assemblyand substantially reduces the necessity for expensive replacementprevalent in conjunction with cast assemblies.

Also, by utilizing aluminum for the main body portions of the huskassembly, electromagnetic interference with the linear variabledifferential transformer is obviated to prevent disturbance in generatedreadout signals. The provision of lubricated bearing pads along theadjacent central peripheral edges of the husk assembly is alsoparticularly advantageous as the same precludes vibration and shock wavedisturbance during system operation.

Inasmuch as the present invention is subject to many variations,modifications and changes in detail, it is intended that all mattercontained in the foregoing description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:
 1. A system for determining the power beingtransmitted through a rotated shaft from a fuel consuming engine,comprising:first means mounted on said shaft for generating a directcurrent signal having a magnitude proportional to torque transmittedthrough said shaft and a polarity corresponding to torque direction,said first means including a husk assembly clamped about said shaft anda linear variable differential transformer carried on said huskassembly; second means coupled with said husk assembly for generating adirect current signal having a magnitude proportional to shaftrotational speed and a polarity corresponding to rotation direction;electronic circuit means having first and second inputs connected toreceive said generated direct current signals from said first and secondmeans, respectively, and an output; said circuit means electronicallymultiplying said signals to produce a direct current signal at saidoutput proportional in magnitude and polarity to the product of saidfirst and second input signals whereby said direct current output signalis linearly representative of the horsepower being transmitted throughsaid shaft in either forward or reverse directions; flowmeter means fordetermining the rate of fuel being consumed by the engine in thetransmission of power through said shaft and providing a direct currentoutput signal representative thereof; and divider means connected tosaid circuit means and said flowmeter means for electronically dividingthe output signal of said flowmeter means by the output signal of saidcircuit means whereby a direct current signal representative ofinstantaneous efficiency is provided.
 2. The invention as recited inclaim 1 wherein said first means and said circuit means are adapted tooperate from a source of direct current operating potential; and whereinsaid system further includes input means adapted to be connected with asource of alternating current operating potential, and power supplymeans connected with said input means for converting said alternatingcurrent operating potential to regulated direct current for said firstmeans and said circuit means.
 3. The invention as recited in claim 2wherein said power supply means includes an isolation transformercoupled at an input to said input means and at an output through arectifier network and a filter network to a direct current voltageregulator.
 4. The invention as recited in claim 1 wherein said firstmeans includes an oscillator for generating an oscillatory signal, andwherein said linear variable differential transformer is coupled withsaid shaft and said oscillator for modulating said oscillatory signal inaccordance with torsional flexure of said shaft, said first meansfurther including a demodulator cooperating with said linear variabledifferential transformer for generating said direct current outputsignal of said first means.
 5. The invention as recited in claim 4wherein said linear variable differential transformer has an inputwinding coupled to said oscillator, an output winding coupled to saiddemodulator, and a core movable with respect to said input and outputwindings in accordance with said shaft flexure.
 6. The invention asrecited in claim 4 wherein said oscillator and said demodulator arecoupled to receive direct current operating potential and to providesaid direct current output signal, respectively, through a plurality ofsliprings and cooperating brushes.
 7. The system as recited in claim 1wherein said circuit means is an integrated circuit.
 8. The system asrecited in claim 1 wherein said husk assembly includes a plurality ofdiscrete axial protrusions equally spaced about the periphery of an endof said husk assembly, and said second means comprises a tachometergenerator mounted adjacent said husk assembly, and a gear wheel coupledwith said tachometer generator, said gear wheel of said tachometergenerator coacting with said protrusions whereby rotation of the shaftimparts rotary movement to said tachometer generator.
 9. The system asrecited in claim 8 wherein said protrusions comprise pins supported onan end wall of said husk assembly and at least partially protrudinglongitudinally therefrom.
 10. The system as recited in claim 1 furtherincludinga torque meter, an RPM meter, and polarity reversing meanshaving a first position for coupling the outputs of said first andsecond means to said torque and RPM meters, respectively, in a positivepolarity sense and a second position for coupling said respectiveoutputs to said meters in a negative polarity sense.
 11. The system asrecited in claim 10 further including calibration means coupled to saidelectronic circuit means and operable to substitute preselected,calibrated signals for the output signals generated by said first andsecond means for use in calibrating the system; and wherein saidcalibration means is connected to said polarity reversing means formaintaining said polarity reversing means in said first position duringcalibration.
 12. The invention as recited in claim 1 further includingovertorque means connected to receive the output signal of said firstmeans for producing an alarm indication in response to said signalexceeding a preselected threshold.
 13. The invention as recited in claim12 wherein said overtorque means includes switch means responsive tosaid threshold-exceeding signal for actuating an alarm device, and apotentiometer connected between said first means and said switch meansto enable preselection of said threshold.
 14. The invention as recitedin claim 13 wherein said switch means comprises a relay, and whereinsaid alarm device is a lamp.
 15. The invention as recited in claim 12wherein said overtorque means produces said alarm indication in responseto said signal exceeding said preselected threshold independent of thepolarity thereof whereby overtorque in either direction is signalled.16. The invention as recited in claim 1 further including reverse torqueindicating means connected to receive the output signal of said firstmeans for producing an alarm indication in response to said signalhaving a negative polarity.
 17. The invention as recited in claim 16wherein said reverse torque indicating means includes an indicatornetwork, and a diode network coupled between said first means and saidindicator network, said diode network supplying an actuating signal tosaid indicator network only when the polarity of said output signal ofsaid first means is negative.
 18. The invention as recited in claim 17wherein said indicator network comprises a direct current power supplyconnected to an operational amplifier having quiescent and activestates, and further comprises a relay controlled alarm device coupled tosaid operational amplifier, said operational amplifier being connectedto said diode network and assuming said active state in response to thegeneration of said actuating signal for operating said alarm device. 19.The invention as recited in claim 18 wherein said alarm device is alamp.